Certain microorganisms are produced in large quantities and can be formulated for various commercial uses. For example, microbial products have been used in agriculture to protect plants from pests and diseases, to improve plant performance and nutrition, and as inoculants for silages. These microbial products must be produced in a way that is efficient, free of contamination, and suitable for maintaining high levels of viable microorganisms. Production of microbial formulations for commercial use requires drying the microorganisms in a way that preserves viability of the microbes, provides a suitable medium for commercial use, and maintains an extended shelf life of the microbial product.
A range of microorganisms have been produced and formulated for commercial use. Examples of commercially formulated microorganisms include strains of Lactobacillus spp. for a variety of food, probiotic, and animal feed uses; entornophagous fungi, such as Beaveria and Metarhizum spp., for control of plant-attacking insects; fungi that protect plants from diseases, such as Trichoderma and Clonostachys spp.; bacteria that protect plants from disease, such as Pseudomonas and Bacillus spp., as well as Rhizobium and Bradyrhizobium; and related bacteria that fix nitrogen through a symbiotic relationship with legumes and fungi, such as Colletotrichum spp., which are used as weed controls by causing disease in weeds. These uses of microorganisms are well documented (Hornby et al., Biological Control of Soil-Borne Plant Pathogens, Wallinford, U.K. (1990); TeBeest, Microbial Control of Weeds, New York, Chapman and Hall (1991); Vurro et al., Enhancing Biocontrol Agents and Handling Risks, IOS Press, Amsterdam (2001)).
Microorganisms formulated for commercial use are usually produced in liquid (submerged) fermentation systems (Jin et al., Principles in the Development of Biological Control Systems Employing Trichoderma Species Against Soil-borne Plant Pathogenic Fungi, p. 174-195 In Leatham, G. F. (ed) Symposium on Industrial Mycology, Mycological Soc. Am., Brock/Springer Series in Contemporary Bioscience (1992); Stowell, “Submerged Fermentation of Biological Herbicides, Microbial Control of Weeds,” D. O. TeBeest. New York, Chapman and Hall (1991); Jin et al., “Conidial Biomass and Desiccation Tolerance in Trichoderma harzianum,” Biological Control 1:237-243 (1992); Jin et al., “Development of Media and Automated Liquid Fermentation Methods to Produce Desiccation-tolerant Propagules of Trichoderma harzianum,” Biol. Cont. 7:267-274 (1996); Agosin et al., “Industrial Production of Active Propagules of Trichoderma for Agricultural Uses,” Trichoderma and Gliocladium, Vol. 2. G. E. Harman and C. P. Kubicek. London, Taylor & Francis pp. 205-227 (1998)) or in semi-solid fermentation.
In all cases, the microorganisms are dried to a level that prevents rapid deterioration of the propagules and/or growth of contaminating microbes (Jin et al., “Conidial Biomass and Desiccation Tolerance in Trichoderma harzianum,” Biological Control 1:237-243 (1992)). Typical drying methods include convective drying (e.g., spray drying or fluidized beds) and static heating. All of these drying methods have the potential to damage sensitive cells or spores of microorganisms. The physiology of spores produced by microorganisms may dramatically influence the methods that can be used to dry the biomass (Agosin et al., “Industrial Production of Active Propagules of Trichoderma for Agricultural Uses,” Trichoderma and Gliocladium, Vol. 2. Harman and Kubicek, London, Taylor & Francis pp. 205-227 (1998)). Similarly, microorganisms differ substantially in the types of resistant propagules that are produced. For example, endospores of Bacillus spp. are hardy enough to withstand relatively high temperatures and rough physical handling without loss of viability. Commercial formulations of these bacteria typically have long shelf-lives. In contrast, some microorganisms produce no resistant spores and exist only as vegetative cells. These microorganisms, which have a shorter shelf-life, include Pseudomonas and Bradyrhizobium spp. Microorganisms which are intermediate in sensitivity include fungal spores, such as conidia, or species of Trichoderma, Clonostaehys, and Colletotrichum. 
One strain of Trichoderma, T. harzianum strain T22, enjoys relatively wide use in commercial agriculture (Harman, “The Myths and Dogmas of Biocontrol. Changes in Perceptions Derived from Research on Trichoderma harzianum T-22,” Plant Disease 84:373-393 (2000)). This microbe has been produced in large quantities and formulated on a clay-based medium. Formulations of this microbe have the disadvantage of being difficult to suspend in water for spray applications, slurry seed treatment formulations, or drench applications in greenhouses. Formulations of this microbe are also limited in their ability to form mixtures with chemical pesticides and biological products. An attempt was made to produce a dry formulation of T. harzianum strain T22 in combination with the chemical fungicide mancozeb. The combination of mancozeb and T22, when applied to potato seed pieces, resulted in improved yield and quality (size) of the potatoes in the succeeding crop. However, the dynamics of potato seed treatment require that any products being applied need to be formulated into a single dry preparation. When T22 and mancozeb were mixed together and stored in a dry formulation, the shelf life of T22 was reduced from about 6 months in the absence of the fungicide to only about 1 month in its presence. This problem has thus far been a major factor as to why T22 is not used significantly as a potato seed treatment.
New and improved methods of producing formulations of viable microorganisms having high activity levels and an extended shelf life are needed. Formulations of microorganisms, to be commercially useful, need to be capable of being suspended in water and mixed with other biological agents or chemical pesticides without toxic implications on the microorganism. Furthermore, it would be useful to formulate biological agents with a food base to help the microbes grow rapidly and to be highly competitive when applied. Current formulations permit growth of competitive microbes on any added food base. Processing methods that avoid damage to delicate microbial cells or spores are also needed.
The present invention is directed to overcoming these and other limitations in the art.